Add a self field to all object types

[rbalicki2]

We should add an unconditional pointer that is a self field on every object type, so you can do something like

fieldGroup: self {
  foo
  bar
  baz
}

• The default behavior will be to create a ... on SelfType inline fragment selection in the merged selection set and in the query, which is fine as an initial pass. But we should eventually understand how to merge that.
• This will eventually be more useful when you can loadably select pointers, use unwraps, etc